1. Field of the Invention
This invention relates generally to liquid level detection systems, and more particularly relates to a liquid level sensor for detecting liquid levels in beverage maker galley inserts, such as in coffee or hot water containers in galley inserts on aircraft.
2. General Background and State of the Art
One conventional technique for determining the level of a liquid in a vessel or container involves mechanically measuring the liquid level with a dipstick or probe which extends into the liquid to be measured. When such techniques are used for measuring liquid level in a server container of a beverage brewing apparatus such as a coffee brewing machine, these techniques require a sensing device to extend into the server container.
Previous mechanical sensing devices, such as for measuring liquid levels in coffee or hot water containers in galley inserts on aircraft, typically have relied on exposed metal-to-metal contacts that would oxidize or become dirty with coffee residue and not function properly. Due to the configuration and physical constraints of such sensing devices, the liquid level sensor is required to have flexible or rotational electrical contacts. The operation of the sensing devices was compromised because of dirt, coffee residue, oxidation and wear, and the exposed electrical connections in such sensing devices typically would become unreliable and intermittent, so that the liquid level sensing devices would require cleaning very frequently. In addition, the liquid level sensing devices would oxidize without use and the beverage maker galley insert would not function if the unit was stored for a period of time. The result was an intermittent electrical contact of the liquid level sensor. If electrical contact failed in the rotating electrical contact joint, the coffee or hot water container could overflow.
It would therefore be desirable to provide a liquid level sensing device that will assure a continuous electrical contact of a moving probe to a wired connection to a controlling circuit board for preventing highly undesirable accidental overflows of liquid containers in galley inserts on aircraft such as may occur with present system of liquid level sensors. The present invention satisfies these and other requirements for aircraft galley systems.